I listed its main features on the development overview page. Basically it's object-oriented, uses the MVC pattern, ActiveRecord as ORM, I18N, theming and much more. They also have a guide with examples for a bunch of its features, and all of its classes are extensively documented in our API reference.

anyway i released a quick update, only file thats changed really is show_donations.php and donate.php

1.3.4 will automatically hide expired donors in the admin panel, with an option to show them. and I also change the regular expression to show only printable characters, instead of striping all non a-z 0-9 chars.
also sorts users by expiration date now
next update will have a login system so you no longer need htaccess, and ill do the prefix support.

If this is incorrect please tell and I will delete/modify post. Also I had a problem with donors not being assigned to servers and the database entries in sb_admins_servers_groups being incorrect. Should have been 1 1 -1 and not 4 8 -1 which is what I am seeing in phpmyadmin.